Bearingless monolithic charge holder for perforating gun

Abstract

A charge holder for use with a perforating gun may include a charge holder body extending in a longitudinal direction, a first coupler provided at a first end of the charge holder body, a second coupler provided at a second end of the charge holder body, and a shaped charge receptacle configured to receive a shaped charge and provided in the charge holder body. The charge holder body, the first coupler, and the second coupler may be integrally formed of a monolithic material. The first coupler and the second coupler may be axially aligned along a first axis. The charge holder body may offset from the first axis such that a center of gravity of the combined charge holder body, the first coupler, and the second coupler is radially displaced from the first axis.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Application No. 63 / 762,348 filed February 24, 2025, United States Provisional Application No. 63 / 832,930 filed June 30, 2025, and United States Provisional Application No. 63 / 946,449 filed December 22, 2025, the entire contents of each of which are incorporated herein by reference.BACKGROUND

[0002] Hydrocarbons, such as fossil fuels (e.g., oil) and natural gas, are extracted from underground wellbores extending deeply below the surface using complex machinery and explosive devices. Once the wellbore is established by placement of casing pipes after drilling, a perforating gun assembly, or train or string of multiple perforating gun assemblies, is lowered into the wellbore, and positioned adjacent one or more hydrocarbon reservoirs in underground formations.

[0003] Assembly of a perforating gun requires assembly of multiple parts. Such parts typically include a housing or outer gun barrel. An electrical wire may also be positioned the housing, the electrical wire being provided for electrical communication with the surface to initiate a percussion initiator, a percussion detonator, a detonating cord, and / or one or more charges within the housing. Where necessary, one or more boosters may also be initiated by the electrical wire. Assembly of the perforating gun typically includes threaded insertion of one component into another by screwing or twisting the components into place. Tandem seal adapters / subs are typically used in conjunction with perforating gun assemblies to connect multiple perforating guns together. The tandem seal adapters are typically configured to provide a seal between adjacent perforating guns. Some tandem seal adapters may be provided internally or externally between adjacent perforating guns, which, in addition to requiring the use of multiple parts or connections between the perforating guns, may increase the length of each perforating gun and may be more expensive to manufacture.

[0004] The perforating gun includes explosive charges, typically shaped, hollow or projectile charges, which are initiated to perforate holes in the casing and to blast through the formation so that the hydrocarbons can flow through the casing. The explosive charges may be arranged in a charge carrier or other holding devices. Once the perforating gun(s) is properly positioned, a surface signal actuates an ignition of a fuse or detonator, which in turn initiates a detonating cord, which detonates the explosive charges to penetrate / perforate the casing and thereby allow formation fluids to flow through the perforations thus formed and into a production string. Perforating gun assemblies may include charge carrying devices configured to swivel or rotate within the gun assembly to achieve a desired firing orientation of the shaped charges.

[0005] In certain types of geological formations, it may be desirable to aim the shaped charges in a particular direction in order to achieve more efficient hydrocarbon extraction. Rotating charge carrying devices or charge holders can gravitationally orient an opening of a shaped charge to a desired firing angle, in horizontal or highly deviated wellbores. There may be a need for further developments in rotating charge holders in order to manufacture the charge holders in a more cost-effective manner and more reliably orient shaped charges in the wellbore.BRIEF SUMMARY

[0006] At least an exemplary embodiment of charge holder for use with a perforating gun may include a charge holder body extending in a longitudinal direction, a first coupler provided at a first end of the charge holder body, a second coupler provided at a second end of the charge holder body, a shaped charge receptacle configured to receive a shaped charge and provided in the charge holder body. The charge holder body, the first coupler, and the second coupler may be integrally formed of a monolithic material. The first coupler and the second coupler may axially aligned along a first axis. The charge holder body may be offset from the first axis such that a center of gravity of the combined charge holder body, the first coupler, and the second coupler is radially displaced from the first axis.

[0007] At least an exemplary embodiment of a perforating gun may include a gun housing extending along a central axis and a charge holder provided within the gun housing. The charge holder may include a charge holder body extending in a longitudinal direction, a first coupler provided at a first end of the charge holder body, a second coupler provided at a second end of the charge holder body, a shaped charge receptacle configured to receive a shaped charge and provided in the charge holder body. The charge holder body, the first coupler, and the second coupler may be integrally formed of a monolithic material. The perforating gun my further include a detonator holder coupled to the first coupler a connector coupled to the second coupler. The first coupler and the second coupler may be axially aligned along the central axis. The charge holder body may be offset from the central axis such that a center of gravity of the combined charge holder body, the first coupler, and the second coupler is radially displaced from the central axis. The charge holder is rotatable around the center axis with respect to the gun housing.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0008] A more particular description will be rendered by reference to exemplary embodiments that are illustrated in the accompanying figures. Understanding that these drawings depict exemplary embodiments and do not limit the scope of this disclosure, the exemplary embodiments will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

[0009] FIG. 1 is a cross section view of a perforating gun according to an exemplary embodiment;

[0010] FIG. 2 is a perspective view of an assembled and disassembled charge holder according to an exemplary embodiment;

[0011] FIG. 3A is a side view of a detonator holder according to an exemplary embodiment;

[0012] FIG. 3B is a perspective view of a detonator holder according to an exemplary embodiment;

[0013] FIG. 3C is a perspective view of a ground plate according to an exemplary embodiment;

[0014] FIG. 3D is a perspective view of a detonator according to an exemplary embodiment;

[0015] FIG. 3E is a cross section of a detonator and detonator holder according to an exemplary embodiment;

[0016] FIG. 4A is a perspective view of a connector according to an exemplary embodiment;

[0017] FIG. 4B is a perspective view of a connector according to an exemplary embodiment;

[0018] FIG. 5 is a perspective view of a charge holder according to an exemplary embodiment;

[0019] FIG. 6A is a side view of a perforating gun according to an exemplary embodiment;

[0020] FIG. 6B is a cross section view of a connector and tandem seal adapter according to an exemplary embodiment;

[0021] FIG. 7 is a perspective view of a retainer clip according to an exemplary embodiment; and

[0022] FIG. 8 is an enlarged perspective view of a portion of a charge holder with retainer clips according to an exemplary embodiment.

[0023] FIG. 9 is a perspective view of a charge holder according to an exemplary embodiment;

[0024] FIG. 10 is an end view of a charge holder according to an exemplary embodiment;

[0025] FIG. 11 is an end view of a guide ring according to an exemplary embodiment; and

[0026] FIG. 12 is a diagram illustrating examples of varying surface roughness according to an exemplary embodiment.

[0027] Various features, aspects, and advantages of the exemplary embodiments will become more apparent from the following detailed description, along with the accompanying drawings in which like numerals represent like components throughout the figures and detailed description. The various described features are not necessarily drawn to scale in the drawings but are drawn to emphasize specific features relevant to some exemplary embodiments.

[0028] The headings used herein are for organizational purposes only and are not meant to limit the scope of the disclosure or the claims. To facilitate understanding, reference numerals have been used, where possible, to designate like elements common to the figures.DETAILED DESCRIPTION

[0029] Reference will now be made in detail to various exemplary embodiments. Each example is provided by way of explanation and is not meant as a limitation and does not constitute a definition of all possible embodiments.

[0030] For purposes of this disclosure, relative terms including, without limitation, “top,”“bottom,”“rear,”“front,”“upper,”“lower,”“above," “below,”“within,” and the like are used to aid the description of, e.g., configurations of features as shown in the accompanying figures, and otherwise as the disclosure makes clear. Such relative terms do not imply any particular dimension or delineation of or between features except where the disclosure makes clear.

[0031] For purposes of this disclosure, terms including, without limitation, “first,”“second,”“third,” and “fourth” are used for descriptive purposes only and without limitation with respect to, e.g., an ordering of process steps, function, or configuration.

[0032] For purposes of this disclosure, “substantially” means generally consistent with the spirit of the disclosure but without limitation to any particular measure.

[0033] For purposes of illustrating features of the embodiments, an exemplary embodiment will now be introduced and referenced throughout the disclosure. It will be understood that this example and other exemplary embodiments described in this disclosure are illustrative and not limiting and are provided for illustrating the exemplary features of a furniture accessory equipped with a power supply.

[0034] FIG. 1 and FIG. 2 shows an exemplary embodiment of a perforating gun 102 and a charge holder 106.

[0035] The perforating gun 102 may include a gun housing 104 that extends in a longitudinal direction, such as along a center axis 144. The gun housing 104 may be machined from a metal such as steel, and may include an inner surface 140 defining an interior space 146.

[0036] A charge holder 106 may be provided within the interior space 146. As seen in FIG. 2, the charge holder 106 may include a charge holder body 108, a first coupler 202 provided at a first end of the charge holder body 108, and a second coupler 204 provided at a second end of the charge holder body 108. The charge holder 106, including the charge holder body 108, the first coupler 202, and the second coupler 204, may be integrally formed as a single piece out of a monolithic material. In other words, the charge holder body 108, the first coupler 202, and the second coupler 204 may be continuously and integrally formed from a single material without any breaks, separation, or assembly. In an exemplary embodiment, the charge holder 106 may be formed from a high-density material such as cast zinc alloy or cast iron. In an embodiment, the zinc alloy may have a density of 7.14 g / cm3. However, it will be understood that the structure is not limited to this material or the casting process. Other high density materials may be used, and other manufacturing processes such as machining or additive manufacturing may be used to produce a monolithic charge holder 106. In an exemplary embodiment, the material of the charge holder 106 may have a density of greater than or equal to approximately 7.0 g / cm3. The monolithic nature of the charge holder 106 may allow for more efficient and cost-effective production of the charge holder 106, as well as reliable gravitational orientation, as described in further detail below.

[0037] The charge holder body 108 may include one or more shaped charge receptacles 110 configured to receive a shaped charge 112. The shaped charge receptacle 110 may be formed as indentations or divots in the charge holder body 108.

[0038] The charge holder body 108 may also include one or more retention protrusions 206 extending from the charge holder body 108 to assist in retaining the shaped charge 112 within the shaped charge receptacle 110. Additionally, one or more retainer clips 134 may be coupled to the charge holder body 108 to assist in retaining the shaped charge 112 in the shaped charge receptacle 110. In an exemplary embodiment, the retainer clip 134 may have a first hook end 208 configured to clip to a rim 212 of the shaped charge 112 and a second hook end 210 configured to couple to a corresponding receptacle on the charge holder body 108. The retainer clip 134 may be formed of a material such as plastic or metal.

[0039] The first coupler 202 may be configured to couple to a detonator holder 114 through means such as a snap, hook, press fit, resilient tabs, threads, hardware fasteners, or the like. For example, the first coupler 202 may include a first coupler end face 214 and a detonator holder receptacle 216. The detonator holder 114 may be inserted into the detonator holder receptacle 216 as explained in detail below with reference to FIG. 3A and FIG. 3B. Similarly, the second coupler 204 may be configured to couple to a connector 116. The detonator holder 114 and the connector 116 may be molded from a material such as plastic.

[0040] As seen in FIG. 1, a first bearing 118 may be fit around the detonator holder 114, and a second bearing 126 may be fit around the connector in order to mount the charge holder 106 within the gun housing 104 of the perforating gun 102. For example, a first inner race 120 of the first bearing 118 may be friction fit or otherwise coupled to the detonator holder 114, and a first outer race 122 of the first bearing 118 may be coupled to the inner surface 140 of the gun housing 104 through friction. A plurality of first ball bearings 124 may be provided between the first inner race 120 and the first outer race 122. Similarly, a second inner race 128 of the second bearing 126 may be friction fit or otherwise coupled to the connector 116, and a second outer race 130 of the second bearing 126 may be coupled to the inner surface 140 of the gun housing 104 through friction. A plurality of second ball bearings 132 may be provided between the second inner race 128 and the second outer race 130. The first bearing 118 and the second bearing 126 result in the charge holder 106 being rotatable relative to the gun housing 104. The charge holder 106 may include projections such as arms or posts for mounting rollers and / or wheels (not shown) in addition to or as an alternative to the first bearing 118 and the second bearing 126, which could be configured to centralize the charge holder 106 and make it rotatable relative to the gun housing 104.

[0041] When mounted in the gun housing 104, the first coupler 202 and the second coupler 204 may be axially aligned on the center axis 144 of the gun housing 104. Alternatively, in an exemplary embodiment in which the charge holder 106 is viewed by itself independent of the gun housing 104, the first coupler 202 and the second coupler 204 may be axially aligned so as define the center axis 144 (i.e., a first axis). The charge holder body 108 may be radially displaced from the center axis 144 such that a center of gravity 148 of the entire charge holder 106 is offset from the center axis 144. Due to the center of gravity 148 being offset from the center axis 144, the weight of the charge holder body 108 will cause the charge holder 106 to rotate around the center axis 144 when the perforating gun 102 is in an approximately horizontal position relative to gravity. In other words, the weight of the charge holder body 108 should always pull the charge holder body 108 toward the bottom of the gun housing 104 when the perforating gun 102 is in the horizontal position.

[0042] Due to this configuration, the number and orientation of the shaped charge receptacles 110 may be configured to achieve a desired perforation pattern depending on the specific geology of the wellbore. In the embodiment shown in FIG. 1 and 2, all of the shaped charge receptacles 110 are oriented such that the shaped charges 112 will aim up when the charge holder 106 is rotatably mounted within the perforating gun 102. However, it will be understood that the disclosure is not limited to this configuration. It will be appreciated that the charge holder 106 could be machined or cast such that one or more shaped charge receptacles 110 are oriented to aim at different angles, or phasing, from each other. For example, a first shaped charge receptacle 110 could be configured to aim up when the charge holder 106 is rotatably mounted, a second shaped charge receptacle 110 could be configured to aim 90 degrees, i.e., horizontal, relative to the first shaped charge receptacle 110, and a third shaped charge receptacle 110 could be configured to to aim 180 degrees relative to the first shaped charge receptacle 110. It will be understood that having varied or phased aiming directions may require the shape of the charge holder 106 to be modified in order to ensure that the center of gravity 148 remains offset from the center axis 144.

[0043] The charge holder body 108 may further include a channel (not shown) extending through the charge holder body 108. The channel may be configured to receive a detonating cord 136 therein. The charge holder body 108 may include small holes or openings extending between the channel and the bottom of the shaped charge receptacles 110 such that the channel, and consequently, the detonating cord 136, are in energetic communication with any shaped charges 112 positioned in the shaped charge receptacles 110. In other words, the energetic communication would allow the detonation of the detonating cord 136 to detonate the shaped charges 112 in the shaped charge receptacles 110.

[0044] In an exemplary embodiment, a detonator 142 may be inserted into a cavity in the detonator holder 114. An exemplary embodiment of a detonator 142 is described in United States Patent No. 11,946,728 issued April 2, 2024, the entire contents of which are incorporated herein by reference. Once properly inserted, the detonator 142 may be proximate to a first end of the detonating cord 136 such that the detonator 142 and the detonating cord 136 are in energetic communication. In other words, activation of the detonator 142 would in turn detonate the detonating cord 136.

[0045] The detonator holder 114 may include a through-wire output (not shown) configured to pass a control signal through to a subsequent perforating gun. This through-wire output may be in electrical communication with a first end of an electrical conductor 138, such as an insulated wire. The charge holder charge holder body 108 may include a passage for accommodating the electrical conductor 138, or the electrical conductor 138 may be clipped or otherwise secured to a side of the charge holder body 108. A second end of the electrical conductor 138 may be in electrical communication with a connector terminal (see conductive slug 412 in FIG. 4A and FIG. 4B as one possible embodiment of a connector terminal) provided in the connector 116 to facilitate passing the signal to the subsequent perforating gun.

[0046] FIG. 3A shows a side view of the detonator holder 114 according to an exemplary embodiment, and FIG. 3B shows a perspective view of the detonator holder 114 according to an exemplary embodiment. FIG. 3A shows that the detonator holder 114 may include a detonator holder body 302, a detonator holder flange 304, and a detonator holder insertion stem 306. The detonator holder body 302 may be generally cylindrical in shape and extend along a longitudinal axis. The detonator holder flange 304 may be attached to the detonator holder body 302 at an end of the detonator holder body 302. An outer diameter of the detonator holder flange 304 may be larger than an outer diameter of the detonator holder body 302. The detonator holder insertion stem 306 may extend from the detonator holder flange 304, and an outer diameter of the detonator holder insertion stem 306 may be smaller than the detonator holder flange 304.

[0047] The detonator holder body 302, the detonator holder flange 304, and the detonator holder insertion stem 306 may comprise a plastic material. In an exemplary embodiment, the detonator holder body 302, the detonator holder flange 304, and the detonator holder insertion stem 306 may be integrally formed as a single piece, for example through injection molding. Alternatively, detonator holder body 302, the detonator holder flange 304, and the detonator holder insertion stem 306 may be formed as two or more separate pieces that are assembled together to form the detonator holder 114.

[0048] FIG. 3A and FIG. 3B further show that the detonator holder 114 may include an outer ground plate 308 provided on or near an exterior of the detonator holder 114 and an inner ground plate 310 provided on an interior of the detonator holder 114. The outer ground plate 308 may be in electrical communication with the inner ground plate 310. In an exemplary embodiment, the outer ground plate 308 and the inner ground plate 310 may be formed of a single piece of conductive material, such as a metal that has been stamped and formed (see FIG. 3C), that extends through the detonator holder body 302. Alternatively, the outer ground plate 308 and the inner ground plate 310 may be formed as separate pieces that are in direct contact or in electrical communication via a wire or other conductive material.

[0049] The outer ground plate 308 may include an outer ground spring 312. The outer ground spring 312 may be formed by punching out and bending a portion of the outer ground plate 308 for example. The outer ground spring 312 may be configured to press against the first inner race 120 of the first bearing 118 (see FIG. 1 and FIG. 2). The first inner race 120 may be in contact and in electrical communication with the plurality of first ball bearings 124, and the plurality of first ball bearings 124 may be in contact and electrical communication with the first outer race 122. The first outer race 122 may be in contact and electrical communication with the gun housing 104, which may be electrically grounded. Accordingly, the outer ground plate 308 and the inner ground plate 310 may be in electrical communication with an electrical ground via the contact between the outer ground spring 312 and the first inner race 120.

[0050] The inner ground plate 310 may include one or more inner ground springs 314. The inner ground springs 314 may be configured to press against detonator ground terminals 320 (see FIG. 3D) provided on the detonator 142 inserted into the detonator holder114. The multiple inner ground springs 314 may provide redundancy to ensure that a solid electrical connection to ground is provided.

[0051] The feedthrough plate 316 may be in electrical communication with the electrical conductor 138. The feedthrough plate 316 may include one or more feedthrough springs 318. The feedthrough springs 318 may be configured to press against detonator feedthrough terminals 322 (see FIG. 3D) provided on the detonator 142 inserted into the detonator holder 114. The multiple feedthrough springs 318 may provide redundancy to ensure that a solid electrical connection to the electrical conductor 138 (see FIG. 1) is achieved.

[0052] The detonator holder insertion stem 306 may be inserted into the detonator holder receptacle 216 of the first coupler 202 until the detonator holder flange 304 contacts the first coupler end face 214 (see also FIG. 2, FIG. 3E, and FIG. 6A).

[0053] FIG. 4A and FIG. 4B show perspective views of a connector 116 according to an exemplary embodiment. The connector 116 may include a connector body 402 that is generally cylindrical in shape and extends in a longitudinal direction. The connector 116 may further include a plurality of connector ribs 404 extending radially from the connector body 402. A connector flange 406 may be provided adjacent to the connector ribs 404 in the longitudinal direction. An outer diameter of the connector flange 406 may be larger than an outer diameter of the connector body 402 and the plurality of connector ribs 404. A first connector protrusion 408 and a second connector protrusion 410 may extend from the connector flange 406 opposite the connector body 402. A conductive slug 412 may be provided within an interior of the connector body 402. The conductive slug 412 may be in electrical communication with the electrical conductor 138. A connector slot 414 may be provided in the connector flange 406 to accommodate passage of the electrical conductor 138 for connection to the conductive slug 412. The connector 116 may further include a detonating cord receptacle 416 configured to receive a portion or an end of the detonating cord 136.

[0054] The connector 116 may be formed as a single piece out of a plastic material, such as through injection molding. Alternatively, the connector 116 may be formed as two or more separate pieces that are assembled together to form the connector 116.

[0055] FIG. 5 shows a perspective view of a charge holder 106 according to an exemplary embodiment. As seen in FIG. 5, the second coupler 204 may include a second coupler end face 502, and a first connector receptacle 504 and a second connector receptacle 506 may be formed in the second coupler end face 502. With reference to FIG. 4A, the first connector protrusion 408 may be configured to be inserted into the first connector receptacle 504, and the second connector protrusion 410 may be configured to be inserted into the second connector receptacle 506 (see also FIG. 6B). The positions of the first connector protrusion 408 and the second connector protrusion 410 and the corresponding positions of the first connector receptacle 504 and the second connector receptacle 506 are rotationally asymmetric, i.e., they only couple in one rotational orientation, in order to help ensure proper orientation of the connector 116 when it is coupled to the second coupler 204.

[0056] FIG. 6A shows a side view of the internal components of a perforating gun 102 according to an exemplary embodiment (see also FIG. 3E and FIG. 6B). As noted above, the detonator holder 114 is inserted into the first coupler 202 until the detonator holder insertion stem 306 abuts the first coupler end face 214 (see also FIG. 2). Once the detonator holder 114 is fully inserted, the first bearing 118 can be slid over the 302 of the detonator holder 114 until the first bearing 118 abuts the detonator holder flange 304. Once the first bearing 118 is in place, a retainer spring 602 such as a snap ring can be inserted to abut against the first bearing 118. The retainer spring 602 may be configured to press against an inner surface and / or a recess or groove of the gun housing 104 (not shown in FIG. 6A) so as to lock in place and fix an axial position of the first bearing 118.

[0057] As further seen in FIG. 6A, the second bearing 126 may be fit over the connector ribs 404 of the connector 116 until the second bearing 126 abuts the connector flange 406. A tandem seal adapter 604 may be coupled to the gun housing 104 so as to abut the second bearing 126 and fix an axial position of the second bearing 126. An exemplary embodiment of the tandem seal adapter 604 may be found in International Application No. PCT / EP2024 / 062360 filed May 3, 2024, the entire contents of which are incorporated by reference.

[0058] FIG. 6A further shows that the retainer clips 134 may include a wire clip 606 configured to receive and hold the electrical conductor 138. The structure of the retainer clip 134 is described in further detail below with reference to FIG. 7 and FIG. 8.

[0059] As seen in FIG. 6B, the tandem seal adapter 604 may include a bulkhead 608. An exemplary embodiment of the bulkhead 608 may be found in United States Patent No. 11,713,625 issued August 1, 2023, the entire contents of which are incorporated by reference. The bulkhead 608 may include a first bulkhead conductor 610 and a second bulkhead conductor 612. The first bulkhead conductor 610 may be in electrical communication with the second bulkhead conductor 612. The first bulkhead conductor 610 and the second bulkhead conductor 612 may be spring loaded. The first bulkhead conductor 610 may be in contact with the conductive slug 412. As described above, the conductive slug 412 is in electrical communication with the electrical conductor 138, which is in electrical communication with the feedthrough plate 316, which is in electrical communication with a feedthrough terminal of the detonator 142. Accordingly, the second bulkhead conductor 612 may provide electrical connectivity to relay a feedthrough signal from the detonator 142 through to a subsequent perforating gun.

[0060] FIG. 7 shows a perspective of the retainer clip 134 according to an exemplary embodiment, and FIG. 8 shows an enlarged perspective view of a retainer clip 134 inserted into the charge holder 106. As seen in FIG. 7, the retainer clip 134 may include a wire clip 606 that defines a wire receptacle 702 configured to receive the electrical conductor 138. This helps to secure the electrical conductor 138 in place so that it does not get entangled with other components or damaged during assembly, transport, and / or wellbore operations.

[0061] The retainer clip 134 may further include a tab 704. As seen in FIG. 7, the wire clip 606 and the tab 704 are adjacent, but it will be understood that the disclosure is not limited to this embodiment and that the wire clip 606 and the tab 704 may be separated or displaced from each other on the retainer clip 134. The tab 704 may be configured for insertion into a corresponding slot 802 in the charge holder 106 (see FIG. 8). The insertion of tab 704 into the slot 802 may provide an additional point of attachment to secure the retainer clip 134 in place.

[0062] FIG. 9, FIG. 10, and FIG. 11 show an exemplary embodiment of a charge holder 106 with a guide ring 902 instead of a second bearing. As seen in FIG. 9, the connector 116 is coupled to the second coupler 204 as noted above. The connector ribs 404 may be inserted through the guide ring 902.

[0063] Looking to FIG. 10 and FIG. 11, the guide ring 902 may include a central hole 1102 and an inner surface 1004 facing the central hole 1102. The guide ring 902 may comprise a metal and may be machined or cast to the desired dimensions. In an alternative embodiment, the guide ring 902 may be formed of a non-metallic material such as ceramic or plastic. The guide ring 902 may have a fixed longitudinal position within the gun housing 104 of the perforating gun 102. For example, a first side of the guide ring 902 may abut against the connector flange 406 of the connector 116, and a second side may abut a retainer spring (similar to the retainer spring 602 illustrated in FIG. 6A). Alternatively, an inner surface of the gun housing 104 may be machined to provide a shoulder or groove for the guide ring 902 to abut against.

[0064] Turning to FIG. 9 and FIG. 10, the connector ribs 404 of the connector 116 may be inserted through the central hole 1102 of the guide ring 902. The connector 116 may be configured to freely rotate within the central hole 1102 such that the charge holder 106 is rotatable relative to the guide ring 902. While not shown in the drawings, the detonator holder 114 may be inserted through a second guide ring provided at the other end of the charge holder 106. Accordingly, the charge holder 106 may be freely rotatable relative to the guide ring 902 and the gun housing 104, such that the charge holder 106 can gravitationally orient itself as described above. Thus, rotation of the charge holder 106 and gravitational orientation may be achieved without the use of ball bearings such as the first bearing 118 and the second bearing 126.

[0065] A number of features may be employed so as to reduce friction between the connector116 and the guide ring 902, thereby facilitating rotation of the connector 116 within the guide ring 902. For example, the connector ribs 404 of the connector 116 may each include a rounded surface facing the inner surface 1004 of the guide ring 902. This may reduce the contact surface area between the connector ribs 404 and the guide ring 902, thereby reducing friction.

[0066] Additionally, the inner surface 1004 of the guide ring 902 may be polished after machining or casting to achieve a smoother surface. For example, in an exemplary embodiment, a surface roughness of the inner surface 1004 may be in a range of 5 μm Ra to 0.1 μm Ra. Alternatively, a surface roughness of the inner surface 1004 may be in a range of 20 μm Rz to 1 μm Rz. FIG. 12 shows a diagram of magnified surfaces at varying machining techniques and surface roughness for illustrative purposes.

[0067] In an exemplary embodiment, the inner surface 1004 of the guide ring 902 may also be coated with a low friction material to facilitate rotation. In an exemplary embodiment, a coefficient of friction between the connector 116 and the inner surface 1004 of the guide ring 902 may be less than or equal to 0.2. Examples of possible low friction materials may include, but are not limited to, silicone, Teflon® coating, low friction ceramics, a Babbitt layer, a carbon layer, molybdenum disulfide, polymer composites, and / or bronze alloys.

[0068] In an exemplary embodiment, a thermal expansion coefficient of the connector 116 may be different from a thermal expansion coefficient of the guide ring 902. Accordingly, the connector 116 and the guide ring 902 may undergo different degrees of expansion as the charge holder 106 is deployed in the wellbore and subject to increasing temperatures. Accordingly, it may be necessary to provide a gap 1002 (see FIG. 10) between the inner surface 1004 of the guide ring 902 and the connector ribs 404 of the connector 116. In other words, an outer diameter 1006 of the connector ribs 404 may be slightly smaller than an inner diameter 1104 of the guide ring 902. Thus, as the connector 116 expands, the gap 1002 allows sufficient room for expansion such that the connector ribs 404 do not create excessive pressing friction against the inner surface 1004 that would inhibit rotation. In an exemplary embodiment, a size of the gap 1002 (i.e., a difference between the outer diameter 1006 of the connector ribs 404 and the inner diameter 1104 of the guide ring 902) may be less than or equal to 2 mm.

[0069] In the above-described embodiments, the connector 116 is rotatable with respect to the guide ring 902. In an alternative exemplary embodiment, the connector 116 may be in a fixed rotational relationship with the guide ring 902, and the guide ring 902 may rotate with respect to the gun housing 104 in order to facilitate the gravitational orientation of the charge holder 106. In this embodiment, an outer surface 1106 of the guide ring 902 and / or an inner surface of the gun housing 104 may employ one or more of the features noted above for friction reduction, such as polished surface to reduce surface roughness or a low friction layer / coating.

[0070] This disclosure, in various embodiments, configurations and aspects, includes components, methods, processes, systems, and / or apparatuses as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. This disclosure contemplates, in various embodiments, configurations and aspects, the actual or optional use or inclusion of, e.g., components or processes as may be well-known or understood in the art and consistent with this disclosure though not depicted and / or described herein.

[0071] The phrases "at least one", "one or more", and "and / or" are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B, or C", "one or more of A, B, and C", "one or more of A, B, or C" and "A, B, and / or C" means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

[0072] In this specification and the claims that follow, reference will be made to a number of terms that have the following meanings. The terms "a" (or "an") and "the" refer to one or more of that entity, thereby including plural referents unless the context clearly dictates otherwise. As such, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. Furthermore, references to "one embodiment", "some embodiments", "an embodiment" and the like are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term such as "about" is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Terms such as "first," "second," "upper," "lower", etc. are used to identify one element from another, and unless otherwise specified are not meant to refer to a particular order or number of elements.

[0073] As used herein, the terms "may" and "may be" indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and / or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of "may" and "may be" indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances the modified term may sometimes not be appropriate, capable, or suitable. For example, in some circumstances an event or capacity can be expected, while in other circumstances the event or capacity cannot occur – this distinction is captured by the terms "may" and "may be."

[0074] As used in the claims, the word "comprises" and its grammatical variants logically also subtend and include phrases of varying and differing extent such as for example, but not limited thereto, "consisting essentially of" and "consisting of." Where necessary, ranges have been supplied, and those ranges are inclusive of all sub-ranges therebetween. It is to be expected that the appended claims should cover variations in the ranges except where this disclosure makes clear the use of a particular range in certain embodiments.

[0075] This disclosure is presented for purposes of illustration and description. This disclosure is not limited to the form or forms disclosed herein. In the Detailed Description of this disclosure, for example, various features of some exemplary embodiments are grouped together to representatively describe those and other contemplated embodiments, configurations, and aspects, to the extent that including in this disclosure a description of every potential embodiment, variant, and combination of features is not feasible. Thus, the features of the disclosed embodiments, configurations, and aspects may be combined in alternate embodiments, configurations, and aspects not expressly discussed above. For example, the features recited in the following claims lie in less than all features of a single disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of this disclosure.

[0076] Advances in science and technology may provide variations that are not necessarily express in the terminology of this disclosure although the claims would not necessarily exclude these variations.

Claims

1. A charge holder for use with a perforating gun, the charge holder comprising:a charge holder body extending in a longitudinal direction;a first coupler provided at a first end of the charge holder body;a second coupler provided at a second end of the charge holder body;a shaped charge receptacle configured to receive a shaped charge and provided in the charge holder body;wherein the charge holder body, the first coupler, and the second coupler are integrally formed of a monolithic material;the first coupler and the second coupler are axially aligned along a first axis; andthe charge holder body is offset from the first axis such that a center of gravity of the combined charge holder body, the first coupler, and the second coupler is radially displaced from the first axis.

2. The charge holder of claim 1, wherein the charge holder body, the first coupler, and the second coupler are integrally cast from a zinc alloy or cast iron.

3. The charge holder of claim 1, further comprising:a detachable retainer clip coupled to the charge holder body and configured to retain the shaped charge within the shaped charge receptacle.

4. The charge holder of claim 3, wherein the detachable retainer clip comprises a wire clip configured to receive and hold a wire.

5. The charge holder of claim 1, further comprising:a channel extending through the charge holder body and configured to receive a detonating cord;wherein the channel is in energetic communication with the shaped charge receptacle.

6. The charge holder of claim 1, further comprising:an electrical conductor extending from the first coupler to the second coupler.

7. A perforating gun comprising:a gun housing extending along a central axis;a charge holder provided within the gun housing, the charge holder comprising:a charge holder body extending in a longitudinal direction;a first coupler provided at a first end of the charge holder body;a second coupler provided at a second end of the charge holder body;a shaped charge receptacle configured to receive a shaped charge and provided in the charge holder body;wherein the charge holder body, the first coupler, and the second coupler are integrally formed of a monolithic material;a detonator holder coupled to the first coupler; anda connector coupled to the second coupler;wherein the first coupler and the second coupler are axially aligned along the central axis;the charge holder body is offset from the central axis such that a center of gravity of the combined charge holder body, the first coupler, and the second coupler is radially displaced from the central axis;the charge holder is rotatable around the center axis with respect to the gun housing.

8. The perforating gun of claim 7, wherein the charge holder body, the first coupler, and the second coupler are integrally cast from a zinc alloy or cast iron.

9. The perforating gun of claim 7, further comprising:a first bearing having a first inner race coupled to the detonator holder and a first outer race coupled to an inner surface of the gun housing; anda second bearing having a second inner race coupled to the connector and a second outer race coupled to the inner surface of the gun housing.

10. The perforating gun of claim 7, further comprising:a guide ring provided at a fixed longitudinal position with respect to the gun housing, the guide ring having a central hole;wherein the connector is inserted through the central hole of the guide ring; andthe connector is configured to rotate within the central hole relative to the guide ring.

11. The perforating gun of claim 10, wherein the guide ring comprises a metal.

12. The perforating gun of claim 10, wherein an inner surface of the guide ring is covered with a material configured to reduce friction between the connector and the guide ring.

13. The perforating gun of claim 10, wherein an inner surface of the guide ring has a surface roughness in a range of 5 μm Ra to 0.1 μm Ra or a surface roughness in a range of 20 μm Rz to 1 μm Rz.

14. The perforating gun of claim 10, wherein:the connector comprises a plurality of connector ribs;the connector ribs are inserted through the central hole of the guide ring;an outer diameter of the connector ribs is smaller than an inner diameter of the central hole of the guide ring.

15. The perforating gun of claim 14, wherein each connector rib of the plurality of connector ribs comprises a rounded surface facing the guide ring.

16. The perforating gun of claim 14, wherein a difference between the outer diameter of the connector ribs and the inner diameter of the central hole is less than or equal to 2 mm.

17. The perforating gun of claim 7, further comprising:a detonator provided within the detonator holder; andan electrical conductor in electrical communication with the detonator; anda connector terminal provided within the connector and in electrical communication with the electrical conductor.

18. The perforating gun of claim 7, further comprising:a detonator provided within the detonator holder;a channel extending through the charge holder body;a detonating cord provided within the channel; anda shaped charge provided within the shaped charge receptacle;wherein the detonating cord is in energetic communication with the detonator and the shaped charge.

19. The perforating gun of claim 7, a detonator provided within the detonator holder, the detonator holder comprising a sensor configured to determine an orientation of the charge holder with respect to a gravitational direction.

20. The perforating gun of claim 7, further comprising:a detachable retainer clip coupled to the charge holder body and configured to retain the shaped charge within the shaped charge receptacle.

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